1. Field of the Invention
The present invention relates to a resin-molded electronic circuit device, method for making the device. More particularly, invention relates to a resin-molded electronic circuit device in which an electronic circuit substrate having electronic components mounted thereon is covered with resin for protection.
2. Description of the Related Art
For example, in an electronic circuit device used in an ignition device of a two-wheeled vehicle for controlling the ignition time, electronic components, an electronic circuit substrate and so on mounted inside are covered with resin to be protected from water, vibrations and so on.
FIGS. 4 and 5 are respectively plan and sectional views of such a conventional resin-molded electronic circuit device. Referring to the figures, a plastic case 1 is provided with openings on the top and front surfaces, and attachment portions 1a and 1a' on the right and left sides thereof. A connector 4 as an external connecting terminal is connected to an electronic circuit substrate 2 having electronic components 3 mounted thereon. This connector 4 has terminal portions 4a surrounded by a protecting portion 4b made of plastic, and is attached to the front side of the case 1 through the protecting portion 4b to cover the front side of the case 1.
A protection resin 5 is filled into the case 1 in which the electronic circuit substrate 2 and the electronic components 3 through the electronic circuit substrate 2 are positioned and the connector 4 is attached to the front side thereof. The electronic circuit substrate 2 and the electronic components 3 are protected from outside moisture and so on by the protection resin 5, and fixed to reduce vibrations. The electronic circuit substrate 2, the electronic components 3, the connector 4 and the protection resin 5 constitute an electronic circuit device 10.
The production method of the electronic circuit device 10 will now be described. After the terminal portions 4a of the connector 4 are connected by soldering or the like to the electronic circuit substrate 2 to which the electronic components 3 are fixed by soldering or the like, the electronic circuit substrate 2 is positioned in the case 1 and the connector 4 is mounted to the front side of the case 1. Then, a resin material is injected and filled into the case 1 and the case 1 filled with the resin material is heated in a furnace to set the resin material, thereby forming the protection resin 5. In this case, since the coefficient of thermal expansion of the protection resin 5 is different from that of metallic portions of the electronic components, (e.g., reads) if the temperature changes, stresses are produced in soldered portions of the electronic components 3 and the electronic circuit substrate 2. In order to reduce the stresses as much as possible, the protection resin 5 is made of a resin material having flexibility.
in the electronic circuit device 10, it is essential to inject the resin material into the case and limit the change in shape of the flexible protection resin 5 to some extent. though it can be thought of that the electronic components 3 and are covered with the protection resin 5 without the case 1 by injecting the resin material into a metal mold under pressure, such pressure injection is not appropriate since it damages the electronic components 3 and when the resin material is injected under pressure.
However, since the above conventional electronic circuit device 10 needs the case 1, the number of components and the number of operation man-hours are increased, and the protection resin 5 typically leaks out from an opening between the connector 4 and the case 1, thereby impairing the outward appearance of the electronic circuit device 10. Furthermore, when the resin material is injected into the case 1, air bubbles form under the electronic circuit substrate 2 and the electronic components, 3 and have a bad influence on the electronic components 3. Still furthermore, when the case 1 filled with the resin material is carried to the furnace, the resin material spills from the case 1. In order to eliminate the above disadvantages, the production of the electronic circuit device 10 needs more man-hours.
Therefore, it is required that such electronic circuit device 10 does not need the case 1.